💧 Fake Growth Data Creates Real Water Plant Problems & Worries Staff
Date: June 3, 2025
Download 6/2/25 City Staff Presentation
Download 4/11/25 Water Plant Memo from OHM Advisors
Introduction
Brett Lenart (City Planning Manager): I'd like to invite our colleagues. We have Sky Stewart, Troy Boffman, and Molly Maciejewski from the city public services division. They also have some consultants with them in tow.
You will recall that we presented to you a summary memo of some of the past analysis that's been done about some of our utility treatment facilities. This same team is in the works of right now doing a lot of analysis of some of our infrastructure systems corresponding with those and so we wanted to provide them an opportunity to address any questions and an overview of some of the work that's going on in that regard.
Next up after that we'll also have a brief opportunity for questions with them. After that we'll be introducing Joe Giant, the city's new economic development director who will be just talking a little bit about his perspective, some of the tasks that he's been set forth with. A lot of this will be very familiar with you from the new approach to economic development report and just the investment in that as a department.
And although included on the agenda, we will not have a presentation from the office of sustainability because it is A2Zero week and they are very very busy.
Chair Donell Wyche: Thank you, Mr. Lenart. [Brief recess for setup]
Main Presentation
Sky Stewart (Chief of Staff, Public Services): Good evening. Thank you for the opportunity to speak with you this evening. My name is Sky Stewart. I'm the chief of staff for the public services area. I manage the systems planning unit which leads the utility infrastructure planning for the city. I'm joined tonight by systems planning utility engineer Troy Bauman, water treatment plant manager Molly Maciejewski, as well as a few of our consultant engineering partners at OHM Advisors who are working with us on utility studies to help us better understand what capacity constraints exist in our water distribution and collection systems today and what improvements are needed to continue to provide for our existing customers and support future growth.
Brett Lenart (City Planning Manager) recently shared a memo with the planning commission that provides an evaluation of the water and wastewater treatment plant capacities under various growth and development scenarios. I'll review the highlights of that memo and also share a little bit more about the other utility planning efforts currently underway that can inform the comprehensive land use plan.
First, I'll provide a quick orientation or refresher of the different parts of the water utility system. I'll review the growth and buildout scenarios that we're using for the utility infrastructure modeling for these studies and then I'll summarize where we are with the planning efforts and what constraints will need to be considered and then I'll open for questions.
Water System Overview
So as a quick orientation or refresher to the different parts of the water utility system we're discussing today, in its most simplistic way I like to think about the water system as moving through the city from the northwest to the southeast generally along the path of the Huron River.
Beginning of our water system starts with our source water. That's where do we get our water? Primarily most of our water comes from the Huron River but we also get water from ground wells a little south of town near the Ann Arbor airport.
That source water is sent through pipes to the water treatment plant. That is where we clean and treat the water to make sure it's safe for drinking. And from there it enters into the transmission and distribution system. It's a network of pipes and storage tanks and pump stations that get the water from the treatment plant to our customers to use in their homes and businesses across our service area.
Then the water is used in the domestic and business uses in all the ways that you can imagine. From there the network of pipes collecting all the water from dishwashers, washing machines, showers, toilets, the pipes, the sanitary collection system pipes carry that waste water to the water resource recovery facility or the wastewater treatment plant to be treated and ultimately returned to the Huron River southeast of town.
Each part of the system has its own infrastructure, its own constraints and investment needs. The memo focused specifically on the plant capacities at the water treatment plant and the wastewater treatment plant, but other studies are underway with a broader scope. I will note that tonight storm water system is not a part of the specific discussion or the analysis that we're going to be talking about today, but I will note that major storm events do have acute impacts on our sanitary system.
Current Planning Efforts
On the drinking water side, the planning for the replacement of the oldest portion of the water treatment plant we call plant one began in 2022. It's nearly 100 years old and it's reaching the end of its useful life. These are long complex planning processes and out of that process has come the water facilities plan. It came in 2024 and that used long-term growth projections from SEMCOG, which is the Southeast Michigan Council of Governments.
And using that information, it resulted in the determination that the existing plant capacity was sufficient for a 50-year horizon, which is a typical planning horizon for major plant projects. This planning for the replacement of plant one is underway now and the tentative schedule is that that construction would start around 2030 and hopefully finish by 2035.
Beginning in 2024, we also began a water distribution plan update to identify the needed improvements to the transmission and distribution pipe network, more than 500 miles of pipes underground. This project is anticipated to be complete by the end of this year. The hydraulic model has been updated and is being used to evaluate the distribution system under both existing conditions and also anticipated future conditions which incorporate a couple of the different scenarios contemplated in the draft comprehensive land use plan.
Growth Scenarios
The growth scenarios modeled in this memo included two buildout scenarios informed by our discussions with the planning staff. They were used to estimate future water demands and wastewater flows based on anticipated population increases. These are also compared to SEMCOG's more modest long-term growth projections.
SEMCOG projections: Annual increase around 200 units per year. To 2050 that'd be about a 9% increase in population.
Low-end buildout scenario: Around 1,200 units per year with an increase of about 66,000 residents or 52% increase in population
High-end scenario: About 1,800 units per year with a 99,000 person increase in population, about 80%.
We do know that per the planning department in the most recent few years the actual unit count has been closer to around 650 units per year.
Key Constraints
Water Treatment Plant Constraints:
Future demands are expected to exceed the current and planned treatment capacity based on those low and high-end buildout projection scenarios
The existing water treatment plant is a landlocked site and cannot support additional capacity on that location
Planning for plant one replacement has been underway for years and is based on that current capacity and current location
The major investments required for plant one are required regardless of growth - it's nearly 100 years old
Source Water Constraints:
85% of our water comes from the Huron River and about 15% comes from wells at Steere Farm near the Ann Arbor airport
We are not permitted to withdraw more water from the Huron River - limited to 40 million gallons a day to maintain the flow of the river during drought conditions (mandated by EGLE)
Future demands in high and low-end buildout scenarios do expect to exceed available source water
Additional supply would be required whether that's a new well field with additional treatment or regional connection
Wastewater System:
Capacity is available to accommodate the projected future growth under dry weather conditions
Limited capacity to accommodate peak wet weather flows under existing and future conditions
The existing landlocked site can't support significant additional capacity - landlocked by a railroad and the Huron River and is also not in the city limits
Summary
The takeaway here is that there are existing constraints in our utility systems. We don't have all the answers to every single one of those constraints. That analysis will continue. There is capacity for growth but it will drive the need for major infrastructure investments particularly when we think about the intensity of development and funding strategies will be needed. The current way that we plan for repairs and replacement of improvements to our existing system can't necessarily fund all future needs.
Q&A Session
Commissioner Dan Adams: Thanks very much. That was really great. I had a question about the benchmark to compare those growth rates against. Your two charts compared the high and low ranges against a SEMCOG rate that we know from planning data is not accurate. It's off by 400% compared to the rate that we're seeing today. What's the right way to understand this?
Sky Stewart: I will say the SEMCOG growth projections that were used in 2022 was at a different moment where we were not building consistently at that rate. I totally agree that we are building at a higher rate right now. But we also know that development isn't linear and so a lot of this is making some assumptions and guesses about the intensity of development and how that will happen. But yes, you were right. There are capacity constraints in all scenarios.
Commissioner Dan Adams: Would it be possible to have those charts updated with the 650 [units per year] so that we can actually see those rates modeled against what we know to be the actual rate of increase?
Sky Stewart: We would not be able to do that for this deck, but we could work with our consultants to work on that analysis.
Commissioner Sara Hammerschmidt: Thank you for this really good presentation. On the water treatment side, where have you been looking into where we could be expanding capacity since it sounds like we cannot expand at the current site? Would it be a second plant somewhere?
Molly Maciejewski (Water Treatment Services Manager): Yes, we are space limited. As you can see, there is that nice green grassy area that looks like we have all sorts of space. That's actually a 6 million gallon underground storage reservoir. So we cannot build on top of that. We have looked at different types of treatment, what could we fit in this footprint, but nothing has shown that we can actually expand capacity. So we would need to look at a whole new location.
As far as source, we know that we're limited at Steere Farm and we're limited at the river. So we would need to look probably to the north for additional well capacity or again consider connection to a regional system.
Commissioner Sara Hammerschmidt: At what point in that trajectory do we run into source water constraints?
Molly Maciejewski: It mimics the water treatment plant. They are designed the same. We have a little additional capacity that we believe that we could get out of the wellfield to the south at the airport. But it would still only get us to the existing treatment plant capacity.
Commissioner Richard Norton: I'm going to maybe be a little repetitive, but just so I'm making sure I'm understanding. If I heard clearly, all of our systems are going to need major upgrades regardless. It's an aging facility. It's an aging system. We're going to need to do it. The question on the right growth rate and what we're planning for is more a question of how soon we have to do that than it is how big the project needs to be to accommodate the growth that we're expecting. Or is it the case? We've been getting feedback from citizens like, "We don't have the capacity to do this and your growth expectations are way out of line and who's going to pay for that?"
Sky Stewart: The plants' capacities are set both by the current source water and what the treatment plant is designed to treat in a day. If we think we're going to surpass that, we will absolutely need to be looking for other locations. We have to make this replacement here to continue providing what we're currently providing, but to go beyond that, we would have to be seeking other treatment and source.
The funding for this is a bit chicken and egg. You can't build it hoping they will come. You need to build it knowing they will come because they have to buy into the system and pay for it. We can't fund full growth. We can fund improvements and repairs to existing system with utility rate dollars but you can't fund speculative future growth with utility rate dollars.
Commissioner Sarah Mills: I got some nerdy questions. Does it matter what kind of housing units - you talked about the adding of the number of units and some of what we're discussing is kind of the different types of housing. I assume water rates are different based on housing type. What's included here?
Sky Stewart: It's a great point. It's very hard to make - you have to make a bunch of assumptions, right? We don't know every single house that will be developed. So you have to make some estimates about what the average daily usage might be and how many people might live in that house. We did build in some assumptions - the assumptions that are built into the current charts that you saw were 2.19 people per unit.
Chris Albers (OHM Advisors): I will say at least on the water side and I believe on the sanitary side it's really reflective of average use in the city right now. So we've gone through looked at the use per person, the kind of peaking factor we see on that use and that is what we projected out.
Commissioner Sarah Mills: Part of this is that there's growth happening in the region, right? And so also when we're thinking about water withdrawal, like you mentioned, we got to think about other people's wells... I'm curious from the water utilities perspective if units from an energy perspective that are built outside the city of Ann Arbor tend to be bigger and so there's more to heat and cool, right? They're driving more because they don't have walkable neighborhoods. And so we shouldn't really like putting a bubble is counterproductive to the world. I'm curious from the water utilities perspective if that is also the case?
Sky Stewart: I would say at a high level, yes. And depending on scenario, we looked at what we would need to do for wells that could be contaminated still or have dioxane hits. So like we know that we may have to expand for those folks, right? So more of that could be necessary. But you're certainly right that we haven't looked at growth in the townships that we currently have contracts with as part of this analysis but it is going to be needed.
Commissioner Richard Norton: Does your stomach turn when you think about the high-end estimates for what population increases could be like? Is the water system or the wastewater system going to crash or yeah, we can accommodate that, we just need to plan for it and make sure we're baking it into our planning efforts?
Sky Stewart: What I can say is that there is capacity for growth. It's the amount and intensity of growth that I think is where we get nervous as utility, as pipe people because you never want basements to back up and you can't have a day where you can't provide water to the customers that you have. And so you do have to be conservative. Thinking about the intensity particularly the very very high end is something that we're worried about. That doesn't mean we can't figure it out. But it is something we are worried about and would cost a lot.
Chair Donell Wyche: Thank you all so much. One of the things that I think I heard that was very clear is you are going to build for the growth of the city as you have as best an understanding of the estimates that you have, right? So you can't build for capacity that isn't here. So as the development occurs that necessitates the growth and then the users help contribute to the funding source to build it out. You have a conservative posture now because of the considerations that you articulated like we cannot say no to the delivery of water and you don't want to overbuild capacity because then you have all this capacity and it's not being utilized.
Sky Stewart: Growth has happened in the whole history of Ann Arbor, right? And so we've always been building as we go. One of the things that we do is when we're planning for the capital plan, when Troy and other engineers are looking at this data, we are looking at this pipe, this 6-inch pipe is getting really old. We need to replace that pipe because it's had a break history or whatever. We are looking at what are the other demands in this area. Where do we think this area is going to be redeveloped and would it need additional - if we're going to be in there replacing that pipe would we want to have additional capacity. So we are looking at incremental ways to create capacity as we're making improvements.
Chair Donell Wyche: Great. Thank you so much.
